1. Field of Invention
The present invention relates generally to heat exchangers, and more particularly, to a weaving apparatus and method used to separate the tubes of a heat exchanger so that spacers that hold the tubes apart can be inserted between the tubes to increase thermal efficiency.
2. Description of the Related Art
Heat exchangers are devices used to quickly and efficiently either cool or heat a gas or liquid (hereafter generically referred to as a “fluid”). A typical heat exchanger includes a pair of header pipes and a plurality of heat exchanger tubes arranged substantially in parallel and adjacent to one another between the header pipes. During operation, fluid is introduced into one of the header tubes. The fluid then travels through the plurality of heat exchange tubes and then passes through the second header pipe to exit the heat exchanger. With a heat exchanger used to cool a hot fluid, the tubes are maintained in a cooling environment. As the hot fluid passes through the heat exchanger, it is cooled by heat transfer through the tubes. With heat exchangers that heat a fluid, the tubes are maintained in a hot environment and the fluid is warmed by heat transfer through the tubes. In general, the larger the heat transfer surface area of the exchanger, the more efficient the device. For this reason, heat exchangers tend to have a large number of tubes. heat exchangers offered by FAFCO Incorporated, Redwood City, Calif., assignee of the present application, have heat exchange tubes made of a thermoplastic material heat welded to the header tubes. When these devices are initially manufactured, the heat exchange tubes are tack-welded together before being welded to the header tubes. This arrangement, however, is less than ideal. The tack-welds between the tubes reduce the overall performance of the heat exchanger because they prevent the free flow of the external environment (typically either a gas or a liquid) from circulating around the tubes. To remedy this problem, the tack-welds between the pipes are broken and spacers are inserted between the tubes forming multiple rows of separate tubes. The spacers physically separate the tubes from one another increasing the circulation around the tubes. For more information on FAFCO's heat exchangers, see U.S. patent application Ser. No. 09/220,639 entitled “Heat Exchanger Having Heat Exchange Tubes with Angled Heat-Exchange Performance Improving Indentations, filed Dec. 24, 1998 and U.S. patent application Ser. No. 09/094,187 entitled “Method and Apparatus for Couling Panel Boards and Tubing to a Header Pipe” filed Jun. 9, 1998, both assigned to the assignee of the present invention and incorporated by reference herein.
The problem with the aforementioned heat exchangers is that the steps of breaking the tack-welds and inserting the spacers are performed manually. Given the large number of tubes per heat exchange unit and their relatively small diameter, this is a very time consuming, labor intensive, expensive process. A weaving machine and method that automates the separation of the tubes is therefore needed.